let ABC be a right triangle at A such that BC=2AB. Find the angle $[\hat{ACB}]$

So let ABC be a right triangle at A such that BC=2AB. Find the angle $[\hat{ACB}]$

How can I find that angle without using cos, sin and other things?

Since I've already figure out how to find it using cos: here's my approach:

We denote $[\hat{ABC}]$ as $\alpha$ so $\cos\alpha=AB/BC=AB/2AB=1/2$

We do cos$^{-1}$ to find the angle ABC then we do 90-ABC to find the angle ACB.

So I'm looking for alternative way.

Thanks so

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